Complete Guide To Lenses

Within serious photography circles it’s generally accepted that the most critical hardware element of a DSLR or compact system camera is the lens you attach to the front of it. For this reason it pays to invest wisely. Lenses come in all shapes and sizes and many are designed for specific purposes, however the first thing to grasp is how the size of your camera’s sensor will affect its stated focal length.

In the days before digital this wasn’t an issue as 35mm film SLRs all used the same 24 x 36mm film stock. A standard 50mm prime therefore produced the same field of view regardless of the camera it was mounted to.

In the digital age, however, sensors come in a number of different sizes, which in turn affects the effective focal length of the lens. This is because sensors that are smaller than 35mm only capture a middle portion of the image generated by a lens.

Put simply, they effectively crop out the sides and magnify the middle. This has the effect of increasing the stated focal length of any given lens. The extent to which each type of sensor does this is usually referred to as its ‘crop factor’.

Because full-frame sensors are the same size as 35mm film they will capture images at the stated focal length of a 35mm lens. APS-C sensors are slightly smaller, however, which gives them a crop factor of 1.5x (Nikon, Pentax and Sony) and 1.6x (Canon). Cameras that use Micro Four Thirds sensors (Panasonic and Olympus) are smaller still, which gives them a 2x crop factor.

Thereby a 50mm prime will shoot at 50mm on a full-frame DSLR, but 75mm on an APS-C equipped camera, and 100mm on a Micro Four Thirds model.

Maximum aperture

Another important consideration when choosing a lens is its maximum aperture. This varies greatly, but as a general rule-of-thumb, lenses with faster maximum apertures, or apertures that remain constant throughout the focal range will be bigger, heavier and more expensive.

The main benefit of having a lens with a faster aperture – say a constant f/2.8 as opposed to f/3.5-5.6 – is that they will allow more light in, enabling you to use faster shutter speeds in low-light situations.

Another benefit of faster lenses is that the higher maximum aperture can be used to create a more limited depth-of-field effect, thereby giving you more artistic control over how much of the image you want to be in focus.

Stabilisation

Image Stabilisation is another useful technology that aims to reduce the image-blurring effects of naturally occurring handshake at slower shutter speeds and longer telephoto settings, where handshake is magnified.

Image Stabilisation technology is usually implemented either inside the lens via a group of optics towards the back of the lens that move to ‘correct’ any detected handshake (Nikon and Canon), or via sensor-shift technology inside the camera body itself (Sony, Pentax and Olympus).

Each manufacturer has a different name for their take on the technology, but essentially they all share a common goal: to make an extra two to five stops of shutter speed available to help keep images sharper.

When choosing a lens you should also consider what you primarily intend to use it for. If you’re looking for a lens that’s great for portraiture then a 50mm or 100mm f/1.8 prime could be ideal, whereas if you’re looking for a single jack-of-all-trades lens to take travelling then an 18-200mm f/3.5-5.6 superzoom may well be your best bet.

Last but not least, remember that prime lenses tend to offer greater levels of sharpness than zoom lenses as they have been precisely engineered to operate at a fixed focal length, whereas the flexibility offered by a zoom tends to come at the cost of some sharpness.

Complete Guide To Lenses – Wideangle Zooms

Wideangle lenses make subjects appear further away and, as a consequence, smaller, than they do to the naked eye. They are useful when you can’t stand back far enough to get everything you want in shot, such as when photographing a large building, an expansive view or large group shot.

But they also produce an apparent perspective distortion in which subjects close to the camera can appear disproportionately larger than those further away – an effect that can be used by the photographer in all sorts of creative ways. They also give the illusion of placing the viewer in the thick of the action, which makes them popular with reportage and street photographers.

Other hallmarks of wideangles include their ability to exaggerate lines and curves, and in some situations distort them, and to produce greater apparent depth of field at a given aperture than longer lenses. The more wideangle the lens, the more pronounced these effects will be.

Although wideangles are available in various fixed focal lengths, our recent tests suggest that a good wideangle zoom, covering a range of focal lengths, is often the smarter bet.

Optically the best ones are on a par with many premium primes, they’re often hardly any bigger and they may even cost less.

Designed for use with APS-C-equipped DSLRs this revamped version of Tokina’s previous fast wideangle zoom adds better lens multicoating and an internal autofocus motor to the mix.

As with the Mk I version it’s a well-made and easy-to-use lens. Despite its limited zoom range, image sharpness is consistently good at all focal length and aperture combinations, apart from when it’s used wide open at maximum wideangle.

Distortion is virtually undetectable too, which makes it well suited to capturing interior spaces with.

This recently released wideangle zoom is designed for use with Fuji’s premium X-Series compact system camera range. Cameras in this range employ APS-C sized sensors, which gives this lens a 35mm focal range equivalent of 15-36mm.

Designed for use on Nikon full-frame DSLRs, the 14-24mm f/2.8 is a fast ultra wideangle zoom that offers a constant f/2.8 aperture throughout its range.

It isn’t possible to use filters with this lens as the convex optic on the front bulges out too much, however the lens does benefit from a Nano Crystal coating to reduce the effects of ghosting and flare, along with a Silent Wave Motor for speedy yet quiet autofocus operation.

As an older lens although there is no built-in Vibration Reduction image stabilisation technology either.

First released in 2003, this wideangle zoom is designed for full-frame cameras, but can also be used with APS-C models, where it offers the 35mm equivalent of 27-64mm.

Given this, you might well wonder why not just stick with a regular 18-55mm kit lens. The answer is simply that the 17-40mm is a professional-grade lens, which is to say extremely tough and well built for constant, daily use.

It also offers a constant f/4 aperture throughout its zoom range, although it lacks any built-in Image Stabilisation technology.

Complete Guide To Lenses – Prime Lenses

Zoom lenses are almost ubiquitous now but fixed focal length, or ‘prime’, lenses continue to be popular because they offer several advantages.

Since they only have to convey a single field of view, as opposed to having to offer a variable range, the optical performance is generally superior.

They tend to be smaller too, and as an extra bonus have wider maximum apertures. If the field of view they offer is the one that you want, and you can fine-tune your cropping simply by moving your position, then they have a lot to offer.

Primes cover the full spectrum of focal lengths from extreme wide to ultra telephoto, but the most useful are those in the 24mm to 85mm range.

This high-specification prime offers a super fast f/1.4 aperture that’s handy for shooting in low light with and, perhaps more importantly, as a creative tool for generating an impressively shallow depth-of-field.

It’s generally accepted that the best focal length for portraiture is between 50-100mm, and this 85mm prime is primarily targeted at portrait enthusiasts.

Canon also makes a faster f/1.2 lens at 85mm, however this will set you back around £1,750. For the money, the slower f/1.8 version delivers impressively sharp images, with MTF curves that remain above the critical 0.25 cycles-per-pixel from wide-open right down to f/16.

While this 50mm prime is designed for use with full-frame Nikon DSLRs, it also makes a half-decent portrait lens when mounted to APS-C equipped camera as this increases its equivalent focal length to 75mm.

In terms of construction it’s a small, lightweight lens that’s easy to stow away in a camera bag and pull out when required.

The lens produces exceptional sharpness when used on FX format cameras, however using the lens with a DX format camera does give rise to chromatic aberrations – at least under lab conditions.

With a 35mm focal length equivalent of 150mm, this lens is targeted primarily at portrait enthusiasts looking to gain a little extra distance between themselves and their subject. As such it neatly complements the M.Zuiko Digital 45mm f/1.8 (£220) to offer extra creative possibilities. With its all-metal construction and silver finish, it’s solidly built and stylish too.

Complete Guide To Lenses – Standard Zooms

Standard zooms, which usually cover the 18-55mm range, are ideal general-purpose lenses. With the standard field of view that equates to the eye at around the 35mm mark on most consumer DSLRs, these lenses go from a little bit wideangle to a little bit telephoto.

This makes them suitable for the majority of the kinds of shots that most people take on a regular basis, from scenic views to portraits.

The kit zoom lenses supplied with most DSLRs do a fairly remarkable job considering that they’re designed to be as cheap as possible to make, so that they add as little as possible to the cost of buying a new camera.

The image quality of these lenses is more than adequate for general snaps but take away the budgetary constraints and it’s possible to produce optics of markedly superior quality.

However if you aspire to produce images of the highest technical standard, possibly at big sizes, you’ll be looking to upgrade the kit lens for a higher-end standard zoom before too long.

They’ll probably be a lot bigger and heavier but they’ll have wider maximum apertures and far superior edge-to-edge resolution, due to the use of technology such as aspherical lens elements and extra low dispersion glass.

Canon’s revamped 24-70mm lens improves on the standard zoom that has long been a favourite of professional photographers. Build quality is excellent and resolution never falls below the critical 0.25 cycles-per-pixel.

In laboratory testing some slight colour fringing does appear at the shortest focal lengths, however this is almost impossible to detect in real-world use.

Overall, this lens represents a solid choice for professionals and well-heeled enthusiasts.

Thanks to the 2x crop factor inherent to Micro Four Thirds sensors, this premium 12-35mm lens provides the 35mm equivalent of 24-70mm.

As a flagship G-series model, the lens offers a constant f/2.8 aperture along with built-in Image Stabilisation.

Image quality is excellent with lab tests producing an excellent set of MTF curves; resolution remains at or above 0.3 cycles-per-pixel between f/2.8 and f/16, and only at f/22 does resolution dip below the critical 0.25 cycles-per-pixel.

Complete Guide To Lenses – Telephoto Zooms

Telephoto lenses have a narrower field of view than wider optics, enabling you to crop in on details and magnify more distant subjects so that they appear closer to you than they actually are.

They’re perfect for photographing things that you can’t get physically close to (at least, not safely) such as elusive wildlife subjects and many sports.

They’re also used for selective in-camera cropping, so you can fill the frame with a single tree in a landscape, or person in a crowd.

Telephoto lenses imbue your images with certain aesthetic traits, such as shallower depth of field, and the sense of compressing distance so that elements further away in your scene seem right on top of closer ones.

Although there’s a wide choice of prime telephoto lenses, zooms offer the huge advantage of allowing you to zoom in or out to get the exact framing you want, which is especially useful given that in many of the situations in which you’d use one you may not be able to freely move around.

As a result, a telephoto zoom is a worthy addition to any photographers lens armory. Here are four great options…

Nikon’s 70-200mm f/4 G telephoto zoom is positioned as a cheaper and lighter alternative to the company’s 70-200mm f/2.8 professional-grade lens; the savings to be made equate to around £600 and 700g in weight.

As the f/4 is a newer model you’ll also benefit from Nikon’s most recent generation of Vibration Reduction image stabilisation technology, which allows you to shoot at up to five stops slower than would normally be possible.

This ultra telephoto zoom is available in a variety of lens mount options and features a built-in Optical Stabiliser, which is all but essential when shooting at the upper limits of its telephoto reach without a tripod.

The lens is fairly bulky and heavy as might be expected, however the internal AF drive system is quick and relatively quiet. Resolution tests in the lab reveal decent, if not quite outstanding results, with sharpness dropping off the further you extend into telephoto territory.

Pushing the telephoto boundaries even further is the Tamron 150-600mm ultra telephoto zoom.

Designed for use with both APS-C and full-frame DSLRs the lens is available to fit a range of manufacturers, and further benefits from a range of built-in features including Vibration Compensation, Image Stabilisation, and an Ultrasonic Silent AF Drive for quiet operation.

Complete Guide To Lenses – Superzooms

Many people are drawn to the idea of a single lens that covers every need from 18mm wideangle to 200mm telephoto and beyond. Such an optic would avoid the need to ever change the lens, so you’d never miss that once-in-a-lifetime shot because you had the wrong one fitted, and of course you’d never get dust on your sensor.

If you suspect there must be a catch then you’re right; there are trade-offs with such lenses. In general, the longer the range, the more the optical quality tends to suffer, with lower contrast, poorer edge sharpness and greater distortion. Superzooms are jacks of all trades but masters of none, and will be outperformed by prime lenses, and many zooms with a shorter range.

The maximum apertures are pretty small too (as low as f/6.3 at the tele end) so you may have to raise the ISO more often to shoot handheld.

However, depending on what you photograph and the level of quality that you demand, you may find these to be sacrifices worth making.

The fact is that at smaller print sizes the average user is unlikely to spot many of these optical deficiencies, so they are fine for users who want reasonably good pictures that won’t be printed too big or studied with a magnifying glass.

If it sounds like a superzoom lens might meet your needs, here are a selection of lenses in a range of mounts that are some of the best going…

The Sigma 18-250mm is an affordable superzoom that offers a little bit more telephoto reach over the 18-200mm lenses typically offered by many first-party manufacturers.

The lens features built-in optical image stabilisation that works quietly and effectively to keep images sharp, while image sharpness impresses too. In lab tests MTF curves remain above the critical 0.25 cycles-per-second all the way down to f/16.

A relatively new addition, this 28-300mm superzoom is designed for full-frame Nikon DSLRS but can also be mounted on APS-C models too, where it will offer the 35mm focal range equivalent of 42-450mm.

The lens features the second generation of Nikon’s Vibration Reduction technology along with Silent Wave Motor technology for quiet focusing. Image quality is very good on the whole, especially when the lens is used at settings of around 50-150mm.

Complete Guide To Lenses – Macro Lenses

The first thing to know about Macro lenses is that most are fixed-focal-length (aka ‘prime’) optics. The most common focal lengths are around 50mm and 100mm, with some in between, though there are also a few at around the 200mm range.

The great benefit of them is that they can also be used for general photography, as they can focus from infinity right down to 1:1 on a single rotation of the focus ring.

One of the main decisions in choosing a macro lens is which focal length to go for. The advantage of the more telephoto macros is that you can obtain your true macro from further away, so if you’re photographing shy subjects such as butterflies you don’t have to be so close to them.

It also means that you won’t be casting a shadow over your own subject and have more space between camera and subject for any lighting that you might want to deploy.

If you think a macro lens might be next up in your kit bag, take a closer look at these four macro lenses in a range of mounts.

There has always been a case for saying that optimum performance is achieved when a lens is designed for one specific purpose, and this is a great example of a lens that does one thing very well indeed.

The 100mm focal length is ideal as it allows for a bit of distance between you and your subject. Although it’s rather large, handling is excellent. Image quality impresses too, with the lens providing MTF results above 0.25 cycles-per-pixel from f/2.8 to f/22, and above 0.4 cycles-per-pixel between f/4 and f/8.

This is a great lens that very much looks and feels like a Leica lens. Because of the 2x crop factor applied to Micro Four Thirds sensors, this provides the 35mm focal range equivalent of 90mm – perfect for most macro situations.

Optical Image Stabilisation (Mega O.I.S) is built into the lens and can controlled from the camera, while the internal AF system is quiet and quite quick.

While resolution does dip at f/2.8 and beyond f/14, at all other settings sharpness remains above 0.3 cycles-per-pixel.

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